We believe in a healthy dose of skepticism, so when headlines shouted that it would soon be possible to diagnose cancer with a single drop of blood, needless to say raised eyebrows were exchanged. While that statement is a touch misleading without further explanation, technically it is not untrue: Scientists are working on a technique that could diagnose cancer using the equivalent of a drop of blood. And their proof-of-concept study looks very promising.
The test is based around tiny cell fragments called platelets, which are the second most common cell found in peripheral blood. They’re normally involved in wound healing and blood clotting to prevent excessive bleeding, but it turns out they can unfortunately go rogue and facilitate cancer progression. We can’t blame them for switching alliances, though; cancer kind of indoctrinates the platelets.
First proposed last year by Robert Weinberg, platelets can be “educated” by tumors by sequestering proteins and various other molecules produced by cancer cells. “In this way, platelets that are usually healing wounds help the tumor do its work,” lead researcher Thomas Wurdinger from VU University Medical Center in Amsterdam explained to IFLScience. “They induce the cell growth switch, so tumors start to migrate towards blood vessels and release cells into the blood stream that can spread. In addition, they promote the growth of blood vessels from the tumor, or angiogenesis.”
This supply of blood helps feed the tumor and prevent the middle from dying of oxygen starvation. “[Platelets] have a central position in tumor growth and spread in the body,” Wurdinger added.
Back in 2011, Wurdinger’s team noticed that these educated platelets have RNA – DNA’s chemical cousin that serves as a template for protein synthesis – derived from tumors and that these sequences are tumor specific. In the present study, published in Cancer Cell, they show that these so-called RNA profiles can be used for cancer diagnostics.
They enrolled almost 300 patients and extracted around six milliliters (0.2 fluid ounces) of blood from each, this was then spun down to isolate the platelets so that RNA could be scrutinized. In this way, they used the equivalent of one drop of blood. From this, they found they could distinguish between healthy patients and those with cancer with 96% accuracy, which is pretty impressive.
Blood samples that have been centrifuged (spun). Fly_dragonfly/Shutterstock
Next, they wanted to know if they could use specially designed computer algorithms to distinguish tumor location from this data, which turned out to be possible. Across six different types of cancer, the researchers could correctly identify the location of the primary tumor with 71% accuracy.
“That’s not sufficient for direct implementation in the clinic,” Wurdinger admits, “but the results could guide further diagnostic tests for confirmation, helping clinicians know where to look and reducing the need for unnecessary, invasive biopsies.”
For example, if a patient has a suspected tumor in the brain, the test could be used to classify with a high degree of accuracy whether this is a primary or secondary metastatic tumor. And if it’s the latter, then the test could help identify the location of the primary tumor in the body, without needing to take a biopsy from the brain, which is difficult and highly risky.
This is by no means ready for the clinic yet, but Wurdinger says they estimate it could hopefully reach that stage within the next five to ten years.